sidered sufficiently distinct from Arothron to merit ge- 

 neric recognition, the name Omegophora Whitley being 

 available for it (by monotypy and original designation, 

 even though not sufficiently diagnosed). 



More importantly, it seems likely to me that a form 

 like armilla which still retained a bifid nasal tentacle and 

 the dorsal flange of the parasphenoid not yet fully devel- 

 oped, could represent the ancestral group from which the 

 typical Arothron arose, for armilla has the most general- 

 ized condition of the frontals (moderate width, evenly 

 and gradually tapering anteriorly), sphenotics (not es- 

 pecially laterally expanded and not expanded antero- 

 dorsally) and prefrontals (moderate size, not greatly 

 downcurved before eye) found among the ArothronAike 

 species. 



It is possible that the pitted cup inner olfactory epi- 

 thelium, as found in typical Arothron, indicates a rela- 

 tionship with Chelonodon, one of whose species {fluvia- 

 tilis) is the only other one among these related genera 

 (Fraser-Brunner's "Tetraodontidae") to have a pitted 

 cup epithelium. However, the skull structure in typical 

 Arothron and Chelonodon is not especially similar and 

 the partial similarly in olfactory epithelium may be for- 

 tuitous, as is, I would guess, the slight similarity in skull 

 structure between C. patoca and A. armilla. 



Figure 272.— Dorsal views of skulls of: left, 

 Chelonodon patoca, 70.6 mm SL, New Guinea; 

 right, C. fluviatilia, 84.7 mm SL, Thailand. 



The monotypic Ephippion of the west coast of Africa is 

 tolerant to fresh and brackish water when young, but 

 adults seem to be found primarily in marine coastal hab- 

 itats. Since Ephippion has a decidedly bifid nasal tenta- 

 cle, as do many species of Tetraodon, several of which 

 live in African fresh waters, and both genera have an up- 

 per lateral line which, usually, is joined by a lower lat- 

 eral line, it has usually been thought that Ephippion is a 

 close relative of Tetraodon with specialized scales. As 

 previously described, the scales of Ephippion even in 

 juvenile stages are larger than those of any other tetrao- 

 dontids except Xenopterus and Chonerhinos, while with 

 increasing specimen size the scales oi Ephippion become 

 enlarged into a partial carapace over the body (except 

 ventrally and to some extent dorsally) between the head 

 and the dorsal and anal fins, the scales of adults being far 

 larger there than in any other plectognaths except os- 

 tracioids. 



The skull of Ephippion differs from that in the two 

 species of Tetraodon studied mostly by having the ante- 

 rolateral wings of the sphenotics heavier and thicker, and 



